Automobile radio and communication system



Nov. 29, 1938.

A. N. GOLDSMITH AUTOMOBILE RADIO AND COMMUNICATION SYSTEM Filed Dec. 9, 1935 2 Sheets-Sheet 1 R M w 1 M A E 0 Riff/V5? INVENTOR.

. ALFRED N. GOLDSMITH MM ATTORNEY Nov. 29, 1938. A. N. GOLDSMITH AUTOMOBILE RADIO AND COMMUNICATION SYSTEM 2 Sheets-Sheet 2' Filed Dec. 9, 1935 GOLDSMITH ATTORNEY.

Patented Nov. 29, 1938 UNITED STATES ATENT DFFICE AUTOMOBILE RADgg AND COMMUNICATION STEM Alfred N. Goldsmith, New York, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application December 9, 1935, Serial No. 53,529

. 8 Claims.

in conjunction with certain additional equip-' ment, for intra-car communication between the occupants of the back of the car and the occu-, pants in the front of the car (for example, the chauffeur). be one-way or two-way as more specifically set forth hereunder.

Automobile radio receivers are generally located at this time in the front of the automobile, their loud speakers being associated with them or closely adjacent thereto. It is known, however, that automobile receivers may be located' a special communication system having loud' speaking characteristics. There are occasions when a caution or a direction to the chauffeur should be promptly and clearly given. My invention is particularly directed toward securing effective communications between the front and back of the car, regardless of intervening partitions and incidental noises, and through the utilization of available circuit elements and loud speakers of one or more radio receivers located in the automotive vehicle.

My invention comprises essentially'the following elements: An assembled radio receiver, (usually in an automotive vehicle), including the power supply, amplifier, and loud speaker thereof; one or more microphones located out of earshot of the receiver in general; and switching means whereby the output of the said microphone may be amplified by the audio-frequency amplifier of the said radio receiver and the resulting output made audible through the radioreceiver loud speaker.

It is a particular feature of my invention that the person controlling the-switching means at the remote microphone can (a) supersede the control of the radio-receiver audio frequency output through the incoming "radio signal, by the output of the remotely-located microphone, and (b) supersede the on-or-ofl. control of the radio receiver as a whole by meansof the remotely The system of communication may cated switch. That is, if the receiver is oif, the remote switch enables it to be turned on; when the,remote switch is restored to the off position, the radio receiver is then itself turned off.

However, if the radio receiver 'is on when the operator of the remotely located switch desires to take control of the radio receiver output by means of his microphone, he can do so but his switch does not either turn on or ofl. the remote radio receiver.

The novel features characteristic of my invention are set forth with particularity in the appended claims. The inventionv itself, however, both as to its construction and mode of operation together with the objects and advantages thereof, will best be understood by reference to the following description taken in connection with the accompanying drawings in which,

Fig. 1 is a schematic circuit diagram of a suitable radio-receiver that may be used in conju ction with my invention. Fig. 2 is a schematic and block diagram of my invention applied to a single receiver in the front of an automobile and communication from the back of the car to the front only. Fig. 3 is a block diagram and schematic circuit showing my invention applied to a two-way connnunication system between the front and the back of an automobile with a receiver located in each portion of the automobile, and Fig.- 4 is a block diagram and schematic circuit of my invention applied to two-way communication between the front and back of the automobile, but with only one receiver, which, for illustration, is placed in the back of the car but could equally well be placed instead in the front.

Referring now to Fig. 1 the receiver circuit there shown comprises a radio frequency amplifier 6, a. detector 1, an audio frequency amplifier 8 and a second audio frequency or power amplifier 9. It will of course be understood that any other known type of receiver, such as the superheterodyne, may be employed. A suitable loudspeaker III is energized from the power amplifier 9. The power supply ll, of which the automobile storage batteryA is a part, is utilized to supply plate potential, grid bias and filament current to the several stages in the conventional manner. The detector stage may be of the gridleak' and condenser type or of the grid bias or power type and is provided in its input with a pair of terminals l-2 and a third terminal 3. It will of course be understood by those versed in the art that the terminals |2--3 may equally as well appear in the input circuit of the audio frequency amplifier. A switch I2 is connected in the power supply circuit between the terminals 4-5 and serves as the on-oif switch for the radio receiver. If an audio frequency input is desired to be amplified by tubes I and/or 8 and 9, it may be injected between terminals l and 2 in the input of detector 1, or alternatively between similar terminals in the input of amplifier 8 (not shown). If terminals I and 3 are short-circuited no radio reception is possible. If 4 is connected to 5, the receiver is operative; if the power supply circuit is opened at 4-5 the receiver becomes inoperative.

The radio frequency portion of the receiver may be rendered ineffective by means other than above described. For example, this portion may be open-circuited as by opening the connection between terminals l and 2, and by injecting the audio frequency input between terminals 2 and 3. Or else the radio frequency portion may be markedly de-tuned from any signal reception position as by introducing resistances in the tuned circuits or shunting the tuning condensers or their trimmers'orboth. Alternatively said portion may be desensitized, as for example, by the usual volume control methods as by varying the grid bias. Alternatively said portion may be rendered ineffective by disconnecting the filament current or the plate voltage or both, for the tubes contained within said radio frequency portion.

In Fig. 2, B represents the back of the car and F the front of the car, the partition being indicated by the vertical dot and dash line. 20 represents the receiver of Fig. 1 as a block. '2l is a microphone which, through battery 22 and transformer primary 23, may produce speech voltages across the terminals of the transformer secondary 24. 25 is a push button or other switch. When depressed, current from battery 28 energizes the electromagnetic relay 26 which operates the 5-pole double-throw switching mechanism 21. The center row of contacts of the switch mechanism are connected'permanently to the receiver.

24- is connected through the switch contacts to terminals 1-2, I is short-circuited to 3, and 4-5 is closed thereby turning on the radio receiver regardless of whether it has been previously in use in-the front of the car or not. If switch 25 is released the switch 21 is thrown in the receive direction R. The receiver is turned off -f'unless it is-already turned on by the occupantof the front of the car) and terminals l2 are connected together to complete the detector input circuit enabling satisfactory radio reception.

To talk to the front of the car an occupant of the back presses switch 25 and talks. When he has completedhis speechhe releases switch 25 thus permitting radio reception in the front of the car if desired. The batteries 22 and 28, it

tween B and F is not all necessary because one side of the car battery may be grounded to the frame of the car thus enabling a return circuit through the frame of thecar if so desired. This The circuit comprising the microphone 2|, micro phone switch 25, relay 26, switching mechanism 21 andreceiver 20 provides communication from the back of the car B to the front F, as in Fig.2,

whereas the circuit comprising the microphone 3|, microphone switch 35, relay 36, switching mechanism 31 and receiver 30 provides communication from the front of .the car F to the back B. Instead of showing the batteries their positive and negative terminals only are indicated.

Resistances 29 and 39 are stabilizing resistances for preventing either microphone 2| or 3| from drawing an excessive current when placed substantially. in parallel with the other during two- 'way communication, thereby preventing equally effective communication in both directions.

Fig. 4 is similar to Fig. 3 except that only one radio receiver 40 is provided, and in this case in the back of the car (although the single receiver in question might equally well be placed in the front if desired), Fig. 4 differs from Fig. 3 primarily in that the loud speakers 48 and .58 have a special connection across their terminals as 3( shown. The loudspeaker 48 is that contained'in the radio receiver 40, and the second loud speaker 58 placed in the front of the car is connected in parallel therewith through the switch 53-. In the reception of radio programs, that is with the switch mechanism 41 in the receive position R; the occupants of both the rear and the front will hear the programs through loudspeakers 48-1nd 58, respectively, unless the cha'uffeur,for example, opens the switch 53 when radio receptionin the front only will be discontinued.

Communication between the front and the rear of the car will be established by manipulation of either push button switch 45-or 55 as explained in connection with Figs. 2 and 3. In each instance the relay 46 will be energized to throw the switch 41 to the transmit position T. In order to avoid the possibility of the chauffeur or other occupant in the front of the car not hearing instructions spoken into the microphone 4|, should the switch 53 be in its open position at the mo- 0 ment, the switch mechanism 41 is provided with a pair of contacts 42-52 which have leads connected to the terminals of switch 53, said contacts being connected together in the transmit position of switch 41, thereby completing the circuit of loudspeaker 58. whether switch 53 is open or closed. The stabilizing resistances 49, 59 serve the same function as resistances 29, 39 in Fig. 3.

I desire not to be restricted to pleasure automobile installations but-regard my invention as applying equally to automobile trucks, trailers, buses, passenger trains, freight trains, and air craft as well as motor boats, yachts, and larger marine crafts. is illustrative. In the case of passenger trains; for example, the separation between the points enjoying communication with each other may be considerable and far in excess of that of an automobile.

What I claim is: f 1. In combination,? a radio receiver having a radio frequency portion and an audio frequency portion, a single power supply source, a local The application to automobiles I switch associated therewithfor energizing and 7 deenergizing said both portions of the receiver, a remote source of audio frequency signals, a first remotely controlled means for energizing thereceiver irrespective of the position of the local switch, a second remotely controlled means for rendering ineffective the radio frequency portion, and a third-remotely controlled means for impressing the remote signal source on the audio frequency portion of the receiver.

2. The invention according to claim 1 wherein a single means is employed to simultaneously actuate the several remotely controlled means.

3. In combination, a radio receiver having a radio frequency portion and an audio frequency portion, a local switch for energizing and deenergizing both said portions of the receiver, a remote microphone source of speech currents and a circuit therefor, switch mechanism associated with both the receiver and the microphone circuit, said switch mechanism being normally in position to open-circuit the microphone circuit and to complete the receiver circuit, and remotely controlled means for actuating said switch mechanism from its normal position to simultaneously energize the receiver irrespective of the position of the local switch,- render ineffective the radio frequency portion, close the microphone circuitand impress the speech currents from said microphone circuit onto the audio frequency portion of the receiver.

4. In combination, a radio telephone receiver and loud speaker permanently associated therewith, a remote loud speaker actuated by the signals from the receiver, means for silencing the radio signals at the remote loud speaker, a microphone in the vicinity of the receiver, means for actuating by the speech currents from the microphone in the vicinity of the receiver, the audio frequency portion of the receiver together with the receiver loud speaker and compulsarily as well the remote loud speaker irrespective of the position of the means for silencing radio signals conducted to such loud speaker, a microphone in the vicinity of the remote loud speaker, means for actuating the audio frequency portion of the receiver and the receiver loud speaker by speech currents from the remote microphone, remotely controlled means for energizing said receiver, remotely controlled means for silencing the receiver radio signals, and remotely controlled means for restoring the audio frequency portion of the receiver and the receiver loud speaker to the reception of radio signals.

5. A system providing two-way communication between two suitably spaced points in a vehicle, such as an automobile, comprising a radio receiver located at each of said points, said receivers each including a radio frequency amplifier, detector and audio frequency amplifier, a microphone and control means at each point, and means operative by either of said control means to energize the receiver located at the point distant from the operated control means and to simultaneously connect the audio frequency portion of said distant receiver to the microphone located at the point where the control means is operated.

6. A system providing two-way communication between two suitably spaced points in 9. vehicle, such as an automobile, comprising a microphone located at each of said points, a single radio receiver including a radio frequency amplifier, detector and audio frequency amplifier, control means at each point, and common means operative by said control means at each point to energize the receiver, to render ineflective the radio frequency amplifier portion and to simultaneously connect both microphones to the audio frequency portion of the receiver.

7. A system according to claim 6 wherein the receiver is provided with a loud speaker at one point for the reproduction of speech currents produced by the microphone located at the other point, a second loud speaker located at said other a point also connected to said receiver for the reproduction of speech currents from its distantly located microphone, local means at said other point for rendering said second loud speaker inoperative, and remotely controlled means for rendering said second loud speaker operative from an inoperative condition.

8. A radio receiver located at a central point, an on-off switch for said receiver at a remote point, a microphone source of speech currents at the remote point, a control key at the remote point, and automatic control mechanism operative in response to'the actuation of said control key for effecting the following operations atthe will of the operator: (1) actuating the on-off switch to energize or deenergize the receiver, (2) to permit normal operation of the radio receiver, and (3) to render ineffective only the radio frequency portion of the receiver and simultaneously therewith to efl'ect transmission of the microphone speech currents from the audio frequency portion of the receiver.

ALFREDN. GOLDSMITH. 

